1) Field of Invention
The present invention relates to aluminum alloy fin material and a heat exchanger for use in an air conditioner, more specifically, an antibacterial and antifungal aluminum alloy fin material and a heat exchanger provided therewith for use in an air conditioner.
2) Description of the Prior Art
Generally, a finned tube heat exchanger is used as a heat exchanger for use in an air conditioner. A finned tube heat exchanger is composed of aluminum fins(hereinafter referred to as xe2x80x9cfinsxe2x80x9d) and round copper pipes(hereinafter referred to as xe2x80x9ccopper pipesxe2x80x9d). Refrigerant fluid pass in the copper pipes which are closely adhered to the fins therein and an air flow pass among the fins in the direction perpendicular to the fluid
When such heat exchanger is used as an indoor evaporator, the refrigerant fluid cooled to 8xc2x0 C. flows in the copper pipes, and the inflow of the air having the temperature of 20xc2x0 C. or higher causes a rise in the relative humidity among the fins.
That is, though the temperature of the surfaces of the fins is maintained at around 10xc2x0 C., it falls below the dew point of the incoming air, and thus drops of water adhere to the surfaces of the fins.
The surfaces of fins in the heat exchanger serve as a good habitat for bacteria and fungi, due to their large area and the humid condition therein. This, therefore, results in such a problem that the air conditioner in operation gives out a bad odor of fungi.
Meanwhile, heat exchanger efficiency is determined by the amount of flow of air. When a heat exchanger serves as an evaporator, drops of water adhere to the surfaces of the fins as described above. Remaining water drops cause increased resistance to the flow of air, thereby reducing the amount of flow of air and entailing decreased efficiencies of not only the heat exchanger but also the air conditioner.
Accordingly, it is important to reduce the resistance to the air flow in view of air conditioner efficiency. Usually, hydrophilic coating film is formed on the fins in order to reduce the resistance. By using such hydrophilic fins, the remaining water on the fin forms a uniform film and the resistance to the air flow is lowered, compared with uncoated fins. Sustaining the hydrophilic property for a long time is therefore highly related to the enhancement of the air conditioner efficiency. In addition, it is also required that the surfaces of the fins are corrosion-resistant enough to maintain such hydrophilic property for a long time.
As described above, it is important how to keep the hydrophilic property and the corrosion resistance for imparting the antifungal and antibacterial properties, to the air conditioner with a heat exchanger provided with hydrophilic fins.
In order to give the antifungal and antibacterial properties, methods of adding antibacterial agent and antifungal agent to a conventional hydrophilic coating system have been used. For example, Unexamined Japanese Patent Publication Hei 1-240688 discloses a heat exchanger A1 fin material with antifungal surface, obtained by forming corrosion resistant coating film on the plate surface of A1 alloy and then hydrophilic coating containing benzimidazolic compounds. And also Unexamined Japanese Patent Publication Hei. 2-101395 discloses an A1 fin material which exhibits its antifungal effect as soon as fungi are generated by the deposition of water, obtained by adding a rapid-acting antifungal agent into the hydrophilic coating film and by adding a delayed-acting antifungal agent into the corrosion resistant coating film.
The common object of the above technologies is to give the fin surfaces a hydrophilic property and also the antibacterial and antifungal properties, keeping the hydrophilic property of the surface.
The above prior arts disclose the method of incorporating antibacterial and antifungal agents into the coating film treated on the fin surfaces. However, in the case of Japanese Patent Unexamined Publication No. 1-240688 where the antibacterial and the antifungal agents are incorporated into the hydrophilic coating film, it is difficult to preserve the hydrophilic property or the antibacterial and antifungal properties at a high level for a long period.
That is, addition of the antibacterial and antifungal agents with high hydrophobic property results in the deterioration of the hydrophilic property, while antibacterial and antifungal agent with high hydrophilic property are easily eluted in dewing water and thus not able to exhibit their properties for a long period.
On the other hand, in the case of Japanese Unexamined Patent Publication No. 2-101395, the delayed-acting antibiotics in hydrophilic coating exhibits their effects after the antibacterial and the antifungal agents in the corrosion resistant coating are eluted into the dewing water and the desired properties therefore can be sustained for a long time. However, when the delayed-acting antibiotics exhibits their effect, the hydrophilic coating has already flowed out and thus sustaining the hydrophilic property for a long time at a high level cannot be obtained.
It is the purpose of the present invention to provide an aluminum alloy fin material whose hydrophilic property and antibacterial and antifungal properties are sustained for a long period at a high level, and a heat exchanger for air conditioner provided therewith.
These and other objects may be attained aluminum-alloy fin material with antibacterial and antifungal properties. This material may be arranged with a first film with average dry thickness of 0.8-2.2 microns, such as a water-soluble resin paint containing 1-30 wt % of (A) bis-(2-pyridylthio)-zinc-1,1xe2x80x2-dioxide particles based on the total solids in the composition of the paint, 40 vol % or more of bis-(2-pyridylthio)-zinc-1,1xe2x80x2-dioxide particles being 1-10 microns in diameter, and a second film with average dry thickness of 0.1-0.6 microns, formed on the first film. The second film may be formed from a mixed aqueous solution such as (P1) vinyl resin with secondary alcoholic structure or derivative thereof, (P2) a water soluble acrylic resin with sulfonic acid group or salt(s) thereof and (B) blocked isocyanate compound, in the ratio of(P1):(P2)=1:8 by weight for solids or in the range of ((P1)+(P2)):(B)=94:6 to 86:14 by wt % for solids.